Not sure if this would be the correct area for this. But I recently just made a 2.5 gallon batch of a stout. And I had a pre-boil gravity of 1.050 with 3.5 gallons of water. And by the end of the boil I had my 2.5 gallons, but I forgot to take a gravity reading before I pitched my yeast.
Is there any general sort of estimation of gravity increase from boil off? Would anyone like to take a guess at what my gravity would have been?